Cured elastomeric materials have a desirable set of physical properties typical of the elastomeric state. They show a high tendency to return to their original size and shape following removal of a deforming force, and they retain physical properties after repeated cycles of stretching, including strain levels up to 1000%. Based on these properties, the materials are generally useful for making shaped articles such as seals and gaskets.
Because they are thermoset materials, cured elastomeric materials can not generally be processed by conventional thermoplastic techniques such as injection molding, extrusion, or blow molding. Rather, articles must be fashioned from elastomeric materials by high temperature curing and compression molding. Although these and other rubber compounding operations are conventional and known, they nevertheless tend to be more expensive and require higher capital investment than the relatively simpler thermoplastic processing techniques. Another drawback is that scrap generated in the manufacturing process is difficult to recycle and reuse, which further adds to the cost of manufacturing such articles.
In today's automobile engines, the high temperatures of use have led to the development of a new generation of lubricants containing a high level of basic materials such as amines. Articles made from elastomeric materials, such as seals and gaskets, are in contact with such fluids during use, and are subject to a wide variety of challenging environmental conditions, including exposure to high temperature, contact with corrosive chemicals, and high wear conditions during normal use. Accordingly, it is desirable to make such articles from materials that combine elastomeric properties and stability or resistance to the environmental conditions.
To meet the demands of the new lubricant technology, a line of fluorocarbon elastomers has been developed highly resistant to the basic compounds found in the lubricating oils and greases. Specifically, cured elastomers based on copolymers of tetrafluoroethylene and propylene have met commercial success. As a thermoset material, the cured fluorocarbon rubber is subject to the processing disadvantages noted above.
It would be desirable to provide an elastomeric or rubber composition that would combine a high level of chemical resistance with the advantages of thermoplastic processability. It would further be desirable to provide methods for formulating chemically resistant rubbers having such advantageous properties.